Influence of Amazonian vegetation on moisture transport toward equatorial America: a modeling perspective

Amazon rainforest is widely recognized as a key source of atmospheric moisture to feed the hydrological cycle at regional and global scales. Recent studies have raised a warning about a discernible lengthening of the Amazon dry season throughout the last few decades, as suggested by observational and modeling analyses. Such lengthening is expected to continue through the 21st Century, according to current climate projections. In particular, previous modeling studies have suggested that changes of vegetation cover could partially explain these longer dry seasons in the Amazon. On the other hand, observational analyses indicate that such lengthening is also related to an enhanced moisture transport toward equatorial America, favoring convection over the equatorial region and subsidence over the Amazon. In this study, we aim to identify if such changes of moisture transport are observed when vegetation cover in the Amazon is changed from forest to savannah. We use the Dynamic Recycling Model (DRM), a 2D Lagrangian model that estimates the transport of water vapor originated as evaporation from different sources. We perform two experiments, one considering a stabilization scenario where the Amazon is covered by tropical rainforest (i.e. similar to current conditions), and a second one considering a stabilization scenario where this forest is replaced by savannah (i.e. an approximation to a possible future scenario). Thus, we track the water vapor from evapotranspiration in the Amazon originated in both scenarios, in order to identify the possible influence of Amazonian vegetation on moisture transport toward equatorial America. This study provides further insights on the relevant role of the Amazon forest as a humidity source to equatorial America.